Railway traffic controlling apparatus



Aug. 25, 1964v cfD. IHRIG 3,145,957

' RAILWAY TRAFFIC CONTROLLING APPARATUS Filed Oct. 15, 1962 2 Sheets-Sheet l l-JTB Locaz'oa Z INVENTOR c ifopd D. I/zpzg'.

HIS HTMRNEY Lama@ I Aug. 25, 1964 c. n; IHRIG 3,145,957

RAILWAY TRAFFIC czoNTRoLLINc: APPARATUS Filed Oct. 15, 1962 2 Sheets-Sheet 2 um awp A v a *51' 9 L gm @N55 A, g@ s. E@ w N Y .Q n S U? a l q N 'Z s Q A 43? HIS ATTORNEY United States Patent O 3,145,957 RAILWAY TRAFFIC CGNTRLLING APPARATUS Clifford ll). Ihrig, Penn Hills Township, Allegheny Connty, Pa., assignor to Westinghouse Air Brake Company, Wilmerding, Pa., a corporation of Pennsylvania VFiled Oct. 15, 1962, Ser. No. 230,352 6 Claims. (Cl. 246-39) My invention relates to railway traffic controlling apparatus and particularly to the type of such apparatus involving train-carried automatic train control devices or cab signals controlled by energy received from the track- Way. More particularly my invention relates to the wayside or trackway parts of such apparatus and is especially applicable to train control or cab signal systems of the coded continuous inductive type.

It is an object of my invention to provide new and improved means for controlling the supply of train control energy to the rails of a stretch of railway track in advance of each train traversing the stretch and, at the same time, to control the supply of train control energy to the rails of said stretch in the rear of each train so as to insure that a distance at least equal to required train braking distance is maintained at all times between each train and the neXt following train.

In accomplishing the above object of my invention I provide, in conjunction with a single track stretch of railway divided into a succession of so-called signal blocks each such block including a series of two or more track sections, a Wayside line circuit comprising a single pair of line conductors for each said signal block, each such pair of conductors being normally energized by steady energy but becoming energized by coded energy when a train occupies any of the track sections included in the respective signal block. For each said track section there is included in series in the associated Wayside circuit the winding of a code following relay which is not actuated by the steady energy normally supplied to the line circuit but which becomes actuated, in response to coded energy supplied to such line circuit, to supply coded train control energy to the track section with which the code following relay is associated.

Other objects and characteristic features of my invention Will become apparent as the description proceeds.

I shall iirst describe one form of apparatus embodying my invention and shall then point out the novel features thereof in claims.

In the accompanying drawings, FIGS. l and 2 when arranged in that order from left to right comprise a diagrammatic view of a track layout equipped with the wayside apparatus forming my invention.

Referring to the drawings, there is shown a stretch of conventional two-rail railway track extending from a first location designated Location l at the west or left-hand end of the stretch through a series of successive locations designated Locations 2, 3 and 4 respectively, to a iifth location designated Location 5 at the east or right-hand end of the stretch. As is readily apparent the rails of said track extend westward from Location l and eastward from Location 5 to additional locations which would be provided with apparatus similar to that to be described for Locations 1 through 5 but which it is not necessary to show for a complete understanding of my invention. This arrangement will be further discussed later in this description and will be readily understood by those skilled in the art.

The railway track stretch shown in the drawings is divided, by insulated joints I provided in the rails of the stretch at each of the Locations l through 5, into a series of track sections designated from left to right 1T through 5T. For purposes of this description the track section to the west or to the left of track section 1T is designated A1T. As indicated by the arrows disposed on the drawings between the rails of the track stretch it is intended that trains traversing the stretch do so in a direction from west to east, that is, from left to right as shown on the drawings.

Each of the track sections 1T through 4T is provided with a conventional normally energized direct current track circuit including a track relay identified by the reference character TR and a track battery identified by the reference character TB, each such reference character being preceded by the digit identifying the track section with which the relay or battery is associated. For eX- ample, the track relay and battery employed in the track circuit for track section 1T are designated 1TR and 1TB, respectively. The designations of the track relays and batteries for the remainder of the track sections will be readily apparent from this example.

There is also provided for each of the track sections, at the exit ends thereof for the direction of traiiic from west to east, a track transformer designated TT preceded by the digit representing the respective track section. For example, the track transformer for track section 1T is designated ITT. Similarly, the track transformer for track section 2T is designated ZTT. From these examples the designations of the transformers associated with the remainder of the track sections will be readily apparent. It will be noted that at each location where a track battery is provided at the exit end of a track section the secondary winding of the associated transformer TT is connected in series with the track battery across the rails of such section, and at each location where a track relay is provided at the exitend of a track section the secondary Winding of the associated track transformer TT is connected in multiple with the track relay across the rails of such section. The track transformers are employed in a manner to be hereinafter described to supply coded alternating current train control energy to the rails of the track sections.

It is believed expedient at this point in the description to point out that, in addition to the direct current sources of track circuit energy mentioned above, there is provided at each of the locations a source of alternating current energy and at Location 4, an additional source of direct current energy. For purposes of simplification of the drawings such sources are not shown therein but the positive and negative terminals of the additional direct current source at Location- 4 are designated by conventional reference characters B and N, respectively. Similarly, the terminals of the alternating current source at each location are designated BX and NX preceded by the digit representing the respective location. For eX- ample, the terminals of the alternating current source at Location 5 are designated SBX and SNX. Each such source of alternating current is considered for purposes of this description to be a cycle source but, of course, any other alternating current frequency could be employed.

The winding of each of the relays employed in my invention is shown in the drawings by a rectangle in the conventional manner, and the contacts controlled by the relays employed are in many instances disposed below the rectangle representing the relay winding and are indicated as controlled thereby by a dotted line extending from each respective winding 4to the associated contacts. Where contacts of relays are not so disposed, the relay by which each contact is controlled is identified by the reference character for the relay being disposed on the drawings above each such contact or group of contacts.

Location 4 (FIG. 2) is a signal control or a code generating location and there is provided at such location a signal control relay designated 4H which corresponds to a home signal control relay provided in railway signaling systems employing conventional wayside signals. However, since my invention relates to a system for supplying train control or cab signal energy to the rails of a railway track stretch, and in which such wayside signals are not necessary, wayside signals are not shown in the drawings. As will become apparent as the description proceeds, Location 1 is a location similar to Location- 4 and a signal control relay, similar to relay 4H and des1gnated 1H, is provided at Location 1. Thus, the length of track between Locations 1 and 4 forms one of the previously mentioned signal blocks. For purposes of simplicity, a full complement of code generating apparatus, such as that shown at Location 4 and to be described is not shown at Location 1. However, the additional apparatus required at Location l will become readily apparent to those skilled in the art as the description proceeds. It should be also pointed out that a complete control circuit for relay 4H at Location 4 is not shown in the drawings, but the manner in which relay 4H is controlled will be readily understood by those skilled in the art by the description of the operation of relay 1H at Location 1.

Locations 2, 3 and 5 are code repeating cut sections and at each such location, in addition to the track circuit apparatus discussed above, there is provided a code following or code repeater relay designated CP preceded by the digit representing the respective location. It will be noted that two such cut sections are shown between Location 1 and Location 4 while a single cut section (Location 5) is shown east or to the right of Location 4. It will become apparent as the description proceeds that the next location east of Location 5 could be another code repeating cut section such as that shown at Location 3, or could be a signal control or code generating location such as that shown at Location 4. The number of code repeating cut sections provided between code generating locations, that is, in each signal block, is dependent on the desired spacing between code generating locations which, as is well known, depends on the speed and the desired spacing between trains traversing the railway. In other words, the location and spacing of the code generating locations, that is, the length of each signal block, is dependent on somewhat the same considerations as would be the locations of wayside signals in conventional railway signaling systems, as well as on the practicable limits of track circuit length. For the operation described herein each signal block should have at least one code repeater cut section.

Referring again to Location 4 (FIG. 2) there is shown, in addition to relay 4H previously mentioned, a code following code control relay V which may be similar to the previously mentioned relays ZCP, SCP and SCP at Locations 2, 3 and 5, respectively; a slow release code control repeater relay VP which is controlled by code control relay V as hereinafter described, and two code generating or code transmitter relays designated 7SCT and 180CT, respectively. Signal control relays 1H and 4H at Locations 1 and 4, respectively, are conventional direct current neutral relays of the type well known in the art. Relays 2CP, SCP, SCP and V are, as previously mentioned, of a type known as code following relays and each, for example, may be similar to the relay shown and described in Letters Patent of the United States 2,659,786, issued November 17, 1953, to Andrew Hufnagel, for Code Following Relay. Repeater relay VP at Location 4 is also a neutral relay of the type well known in the art but provided with a slow release feature to make the armature of the relay slow to release upon the deenergization of the winding of the relay. This slow release feature of relay VP is indicated in FIG. 2 (Location 4) of the drawings by an arrow drawn through the movable portion of contact a of the relay with the head of the arrow pointed in the downward direction, that is, the direction in which the relay and therefore such contact, is slow acting. The circuits employing said contact a will be discussed hereinafter.

The prefixes 7S and 180 of the code transmitteror code generator relays CT and 180CT provided at Location 4 designate the code rates of each of these relays. Such relays are also well known in the railway signaling art and the code rate of each such relay refers to the number of closures per minute of the front or back contacts of the relay when the winding of the relay is energized. As shown in FIG. 2 of the drawings, the windings of the code transmitter relays are continuously energized by having the positive and negative terminals B and N of the direct current source at Location 4 connected to the relay windings and, therefore, the contacts of each relay are continuously operating at the respective code rate of the relay. The contacts of such relays are, therefore, illustrated by showing solid lines for the movable portion of the contacts closed against the front contact points, thereby indicating that the windings of the relays are continuously energized; and by showing dotted lines for the movable portions of the contacts in the open condition of the front contacts, thereby indicating that, although the relays are continuously energized, the contacts are intermittently operating at their respectvie code rates. This is believed apparent from an examination of the drawings.

It is expedient to point out at this time that all trains to traverse the track stretch shown in the drawings are provided with cab signal or train control apparatus which is responsive to pulses of code alternating current supplied to the track rails in advance of each train. Such apparatus forms no part of my present invention and is therefore not shown in the drawings. However, in order to provide a complete understanding of the wayside apparatus forming my invention, each train to travel the track stretch may be considered to be provided with traincarried train control apparatus similar to that shown in Letters Patent of the United States 2,336,766, issued December 14, 1943, 'to Leslie R. Allison and Carl Vol2, for Railway Tratiic Controlling Apparatus, except that the R relay and its associated apparatus in the decoding unit DU shown in FIG. l of the patent are not necessary for the system herein described. This will be readily apparent to those skilled in the art since the apparatus of my invention does not show the use of current coded at the code rate.

When there are no trains in the track stretch shown in the drawings, relay 1H at Location l (FIG. l) is normally maintained picked up by a circuit which extends from terminal B of the direct current source at Location 4 (FIG. 2), through the winding of relay V, over the back point of contact a of relay VP, front contact a of track relay 3TR, line conductor 10, front contact a of track relay ZTR at Location 3 (FIG. l), the winding of relay ZCP, the front point of contact a of track relay llTR at Location 1, and through the winding of relay 1H and over line conductor 11 to the negative terminal N of the direct current source at Location 4. It is pointed out that the winding of relay V at Location 4 and the winding of relay ZCP at Location 2 are so selected, in conjunction with the winding of relay 1H and the value of the direct current source provided at Location 4, that the completed circuit just described is so proportioned that relays V and ZCP will not become picked up under the normal condition of such circuit.

It will be readily understood that relay 4H and relay SCP at Locations 4 and 5, respectively, are, as previously mentioned, controlled in a manner similar to relays 1H and ZCP, respectively, and, therefore, relay 4H is normally also in the picked-up condition.

It will now be assumed that a train traveling in the eastward direction over track section AIT (FIG. l) enters track section 1T and releases track relay 1TR causing the front and back points of contact a of relay 1TR to open and close respectively. Such actuation of contact a of relay 1TR opens the previously described energizing circuit for relay 1H and again completes such circuit excluding the winding of such relay. The windings.

of relay ZCP at Location 2 and relay V at Location 4 are so proportioned in conjunction with the winding of relay 1H that, with the resistance of the Winding of relay 1H removed from the circuit, relays ZCP and V will become picked up by the energy from the direct current source at Location 4. This control circuit is identical to that previously described except that the circuit now extends over the back point of contact a of track relay 1TR and, as mentioned above, the winding of relay EH is excluded from the circuit.

Referring now to Location 4, when relay V becomes picked up as described above, it closes its front contact a and completes a pickup circuit for relay VP. This circuit extends from terminal B of the direct current source over front contact a of relay V and through the winding of relay VP to terminal N of the direct current source. Relay VP thus also becomes picked up.

When relay VP becomes picked up, the previously described circuit through the back point of Contact a of the relay is opened and a circuit through the front point of contact a of the relay is closed. This circuit extends from terminal B of the direct current source through the winding of relay V, front contact a of code transmitter relay ISQCT, the front point of contact a of relay 4H, the front point of contact a of relay VP, front contact a of track relay STR, conductor 10, front contact a of relay ZTR (Location S the winding of relay ZCP (Location 2), the back point of contact a of track relay TR and thence over conductor 11 to terminal N of the direct current source at Location 4. Relays V and ZCP at Locations 4 and 2, respectively, now follow the coding operation of contact a of code transmitter relay lfitCT and operate their contacts at the 180 code rate. As previously mentioned, relay VP is provided with a slow release feature and bridges the open periods of contact a of relay V in the code following operation. Thus, at this ti1ne,the circuit just described `remains closed at the front point of contact a of relay VP.

At Location 2 relay ZCP, as described, follows the coding operations of contact a of relay ltlCT at Location 4 and opens and closes its front contact a at the 180 ycode rate to control the supply of pulses of alternating current energy at such rate to the rails of track section 1T.

The control circuit for such energy extends from terminal ZBX of the alternating current source at Location 2, over said front contacta of relay 2CP and through'the primary winding of transformer ITT to terminal ZNX of said alternating current source. As will be readily understood, such intermittent energization of the primary Winding of transformer lTT Will induce pulses of alternating current energy at the 180 code rate in the secondary winding of transformer ITT, and such pulses will flow through battery 1TB and be supplied across the rails of track section 1T to supply train control energy to the aforesaid train as it traverses that track section.

It will now be assumed that the train traversing track section 1T enters track section 2T and releases track relay ZTR at Location 3. When such action takes place, track relay ZTR opens its front contact a and closes its back contact b. This operation disconnects the Winding of relay ZCP from the previously traced circuit, and connects the winding of relay SCP into such circuit in the place of the Winding of relay ZCP. Relay ZCP ceases to follow the coding action of contact a of relay 180CT at Location 4 and relay SCP starts such code following operation. It is pointed out that the winding of relay SCP (as Well as the winding of relay SCP at Location 5) is selected with the same considerations as the winding of relay ZCP.

The code following operation of relay SCP actuates contact a of that relay at the 180 code rate to control the supply of pulses of alternating current at such rate to the rails of track section 2T. This control circuit extends from terminal SBX of the alternating current source at Location S over the front point of contact a of relay SCP and thence through the primary winding of transformer ZTT to terminal SNX of such alternating current source. Such intermittent energization of the primary Winding of transformer 2TT induces pulses of alternating current at the code rate in the secondary winding of transformer ZTT, and such pulses are supplied across the rails of track section 2T to supply train control energy to the train at it traverses that track section. The pulses of train control energy to track section 1T are terminated at this time since front contact a of relay 2CP is no longer following the coding operation of contact a of relay ltlCT. It will be noted that contacts a of relays ZCP and SCP, as well as contact a of relay ECP at Location 5, are shown with the solid lines representing the movable portion of each such Contact in the downward or normally open position. This represents the normal condition of the contacts of each such relay. However, the dotted lines showing the movable portion of the contacts in the upward or closed position indicate that such contacts operate, at times, in a code following manner.

The train traversing the track stretch now enters track section ST and releases track relay STR (Locacation 4). The release of track relay STR opens contact a of that relay in the previously described control circuit for relay SCP and that relay ceases to follow the coding operation of contact a of relay 180CT. Similarly, the control circuit for relay V at Location 4 is open at front contact a of relay STR and relay V also ceases to follow the 180 code. Relay VP subsequently releases and again opens the front point of its contact a and closes the back point of such contact. The train may have previously vacated track section 1T or may at this time do so. Such action causes relay lTR to again become picked up and close the front point of its contact a to again connect the winding of relay 1H to the previously described control circuit. However, no other operation of the line circuit apparatus occurs since, as previously mentioned, the line circuit is open at front contact a of relay STR.

The release of relay STR when the train enters track section ST also closes back contact b of the relay and completes a circuit for energizing the primary winding of transformer STT with alternating current energy at the 180 code pulse rate. This circuit extends from terminal 4BX of the alternating current source at Location 4 over front contact b of relay ISCT, front cont-act b of relay 4H, back contact b of relay STR and through the primary winding of transformer STT to terminal 4NX of the alternating current source at Location 4. Pulses of alternating current at the 180 code rate are thus induced in the secondary winding of transformer 4TT and are supplied across the rails of track section ST to supply train control energy to the train as it traverses that track section. The subsequent vacating of track section 2T by the train merely causes relay ZTR to again become picked up, and open the circuit to relay SCP (Location 3) and again close the circuit to relay ZCP (Location 2). No other operation takes place at this time since the control circuit for relay 1H remains open at front contact a of relay STR.

When the train enters track section 4T, relay 4TR releases and transfers its contact a, included in a control circuit for relay 4H, from its front contact point to its back contact point. As previously mentioned, the control circuit for relay 4H is similar to that for relay 1H at Location l and includes in series therewith the winding of relay SCP at Location 5. Such circuit extends eastward from Location 5 over conductors 12 and 1S to an apparatus control arrangement similar to that shown at Location 4. It will thus be readily apparent that the entrance of the train into track section 4T, and the con- SCP, to control the supply of train control energy across the rails of track section 4T and, consequently, to the train traversing that track section.

The entrance of the train into track section 4T and the release of relay 4H opens front contact b of that relay in the previously described energizing circuit to the primary winding of transformer STT and the train control energy supplied across the rails of track section 3T is interrupted. The release of relay 4H also opens, at the front point of contact a of that relay, the circuit connected to contact a of relay IStlCT, and closes at the back point of contact a of relay 4H a circuit to contact a of code transmitter relay 75CT. When, therefore, the train subsequently vacates track section 3T and relay STR again becomes picked up and closes its front contact a, a circuit is prepared for supplying code pulses at the 75 code rate to the two wire line circuit extending to Locations 1, 2 and 3, such circuit becoming completed if a following train enters track section 1T while the rst mentioned train occupies track section 4T or 5T or any other track section provided betwen Location and the next code generating location to the east of Location 5.

As mentioned above, if a second train should enter track section 1T while the first mentioned train occupies track section 4T or any other track section provided between Location 4 and the next code generating location to the east, relay 1H at Location l will be released as before, relays V and VP will become picked up as previously described, and then relay 2CP at Location 2 and relay V at Location 4 will follow the 75 code pulses supplied over the front point of contact a of relay VP and the back point of contact a of relay 4H to the line circuit including conductors 1t) and 11. So long as the first train occupies any of the track sections between Location 4 and the next code generating cut sectionto the east, that is, the next signal block, the second train will, while traversing track sections 1T and 2T, continue to receive train control energy at the 75 code rate. However, when the second train enters track section 3T under such conditions, it will receive no coded train control energy from the rails and the train will be controlled tol stop. This is due to the circuit to the primary winding of transformer STT being open at front contact b of relay 4H so long as the first train occupies the length of track between Location 4 and the next code generating location to the east. If, however, the second train is traversing track section 1T or 2T when the rst train vacates said length of track, that is, the next signal block to the east of Location 4, relay 4H will again become picked up, and the second train will immediately receive train control energy at the 180 code rate and will continue to receive such energy when it enters and as it traverses track section 3T.

From the foregoing description it is apparent that, with the apparatus of my invention as shown in the drawings of this application, I have provided an economical system of wayside apparatus for supplying train control energy to the rails of a stretch of railway, such apparatus being controlled by a single pair of wayside conductors which are normally energized by steady energy but which become energized by coded energy to control the supply of train control energy to the rails of each track section in the stretch according as each such section becomes occupied by a train. It is readily apparent that the apparatus of my invention is especially adaptable to railway traic control systems in which no wayside signals are employed.

While I have shown and described only one form of apparatus embodying my invention, it should be understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

l. Apparatus for supplying train control energy to the rails of a stretch of railway track including a succession of signal blocks, said apparatus comprising, in combination:

(a) a series of track sections in each said signal block,

(b) a track circuit including a normally energized track relay for each said track section,

(c) a control relay associated with the entrance end of each signal block,

(d) a code following relay associated with the exit end of each track section,

(e) a source of direct current energy associated with the exit end of each signal block;

(f) a two conductor line circuit extending between the ends of each of said signal blocks, each said circuit including in series said source of energy associated with the respective signal block, the windings of the control relay and at least one of the code following relays associated with the signal block, and front contacts of the track relays for the track sections in the signal block, such apparatus included in the line circuit being so proportioned that so long as the winding of the control relay is included in the line circuit only such control relay becomes picked up in response to energy from the source associated with the signal block;

(g) means including a back contact of the track relay for each track section in one of said signal blocks, except the last track section in such block, for bypassing the winding of the control relay in said line circuit for that signal block, the apparatus included in the line circuit being so proportioned that the remaining relays included in such circuit become picked up in response to the source of energy for the signal block when the winding of such control relay is bypassed;

(h) a slow release relay associated with the exit end of said one signal block,

(i) a control circuit for said slow release relay including a front contact of the code following relay associated with the last track section in said one signal block;

(j) means controlled by said slow release relay for interrupting the steady energization of the line circuit for said one signal block and energizing such line circuit by pulses of energy at a first or second code rate according as the control relay associated with the next succeeding signal block is picked up or released, respectively;

(k) means responsive to the code following operation of each of the code following relays in said one signal block, except the code following relay assoclated with the last track section in such block, for supplying pulses of train control energy across the rails of the exit end of the track section with which each respective code following relay is associated; an

(l) means, including a back contact of the track relay for the last track section in said one signal block and a front contact of the control relay associated with the next succeeding signal block, for supplying pulses of train control energy at said rst code rate across the rails of the exit end of such last track section.

`2. A system for supplying train control energy to the ralls of a stretch of railway track including a succession o of signal blocks, said system comprising, in combination:

(a) a series of track sections in each said signal block;

(b) a signal control relay and a code control relay associated with the entrance and exit ends, respectively, of each signal block;

(c) a code following relay associated with the exit end of each said track section except the last of said series of track sections within each signal block,

(d) a source of direct energy at the exit end of each signal block;

(e) a two conductor line circuit extending between the ends of each signal block, each such circuit including in series the source of energy for that signal block, and the windings of the code control relay,

winding of the signal control relay associated with that block excluded from the circuit, such circuit and the windings of the remaining relays associated with 10 (b) a code control relay at a rst location at the exit end of one of said track sections, (c) a signal control relay at a second location at the entrance end of another of said track sections,

the Signal COllflO1 relay, and at least 011e 0f the 00de 5 (d) a code following relay at the exit end of each track following relays associated with that signal block, section between said locations;

Said Circuit, windings, and Source of energy being S (e) a two conductor circuit extending between said 1eprOpOrtiOIled that S0 10I1g 21S the Winding 0f the Sgcations and including in series the windings of said nal control relay is included in the circuit only such relays, said line circuit being normally energized by control relay becomes picked up in response to said steady energy and said windings being so proper. energy; tioned that only said signal control relay becomes (f) means responsive to the occupancy by a train of picked up in response to such steady energy;

each track section except the last track section in a (f) means responsive to the occupancy by a train of signal block for opening said line circuit for that each said track sections for interrupting said circuit block and thereafter closing the circuit with the l5 and thereafter again completing said circuit excluding the winding of said signal control relay, the windings of said relays and said circuit being so proppr tioned that with the winding of the signal control that block being so proportioned that such remaining relays included in the circuit become picked up 2O in response to the energy from the direct current source for the block when the winding of the signal control relay is excluded from the circuit;

(g) means responsive to the picking up of the code control relay for a signal block for changing the steady energy supplied to the line circuit for that block to pulses of energy at a 'first or a second code rate according as the signal control relay associated with the next succeeding block is picked up or released, respectively;

(h) means responsive to the code following operation of each of the code following relays in a signal block for supplying pulses of train control energy across the rails of the exit end of the track section with which each respective code following relay is associated; and

(i) means responsive to the occupancy by a train of the last track section in each signal block, and controlled by the signal control relay for the next succeeding signal block, for supplying pulses of train control energy at said irst code rate across the rails of the exit end of such last track section so long as such signal control relay is picked up.

3. In combination:

(a) a length of railway track divided into a series of track sections,

(b) a signal control relay at the entrance end of the rst of said series of track sections,

(c) a code control relay at the exit end of the last of said series of track sections,

(d) a code following relay at the exit end of each except the last of said series of track sections;

(e) a two conductor line circuit for said length of track,

relay excluded from the circuit lthe other relays become picked up in response to the steady energy;

(g) means responsive to the picking up of said code control relay for interrupting said steady energy and supplying coded energy to said line circuit, and

(h) means responsive to the code following operation of each said code following relay for controlling the application of train control energy to the rails of the exit end of the track section with which that relay is associated.

5. In combination:

(a) a stretch of railway track divided at preselected locations into a succession of track sections, prede- Itermined ones of such locations comprising code generating locations and at least one of the remaining preselected locations being between successive ones of said code generating locations;

(b) a signal control relay and a code control relay at each code generating location,

(c) a code following relay at each said remaining preselected location;

(d) a two conductor line circuit extending between a rst code generating location and the next preceding code generating location, said circuit including in series the winding of the code control relay at said rst code generating location, the winding of the code following relay at each location between said rst and said next preceding code generating locations, and the winding of the signal control relay at said next preceding code generating location said circuit being normally energized by steady energy, and said circuit and the windings of the relays included in said circuit being so proportioned that only the signal control relay at said next preceding code generating location is picked up in response to said said circuit being normally energized by steady energy and including in series the windings of said relays, said windings and circuit being so proportioned that only so long as the winding of said signal control relay is included in the circuit only the signal steady energy;

each track section between said irst and said next preceding code generating locations for excluding the winding of the signal control relay at such next control relay becomes picked up in response to the steady energy;

(f) means responsive to the occupancy by a train of each track section for excluding the winding of said signal control relay from said circuit,

(g) means thereafter responsive to the picking up of said code control relay for changing the energization ing the steady energy supplied to such circuit and of said circuit from steady energy to coded energy, suppling pulses of coded energy to the circuit, and and (g) means responsive to the code following operation (h) and means responsive to the code following operaof each code following relay included in said line tion of each code following relay for supplying coded circuit for supplying pulses of train control energy train control energy to the rails of the exit end of to the rails of the exit end of the track section assothe track section associated with the respective code ciated with that code following relay. following relay. 6. Apparatus for supplying train control energy to` the 4. In combination: rails of a stretch of railway track divided by insulated rail (a) a stretch of railway track divided into a succession joints into a succession of signal blocks, each signal block of track sections, being further divided by insulated rail joints into a series location from said line circuit, said line circuit being so proportioned that such exclusion of said winding causes the picking up of the code control and the code following relays included in the circuit;

(f) means responsive to the picking up of the code control relay included in said line circuit for interruptof track sections, said apparatus comprising, in combination:

(a) a track circuit including a normally energized track relay for each said track section,

(b) a control relay associated with the entrance end of each signal block,

(c) a code following relay associated with the exit end of each track section,

(d) a source of direct current energy associated with the exit end of each signal block;

(e) a two conductor line circuit extending between the ends of each of said signal blocks, each said circuit including in series said source of energy associated with the exit end of the respective signal block, the windings of the control relay and at least one of the code following relays associated with the signal block, and front contacts of the track relays for the track sections in the signal block, such apparatus included in the line circuit being so proportioned that so long as the winding of the control relay is included in the line circuit only such control relay becomes picked up in response to energy from the source associated with the exit end of the signal block;

(f) means including a back contact of the track relay for each track section in each signal block, except the last track section in such block, for bypassing the winding of the control relay in said line circuit for that signal block, the apparatus included in the line circuit being so proportioned that the remaining relays included in such circuit become picked up in response to the source of energy for the signal block when the winding of such control relay is bypassed;

(g) a slow release relay associated with the exit end of each signal block,

(lz) a control circuit for each said slow release relay including a front contact of the code following relay associated with the last track section in the respective signal block;

(i) means controlled by each slow release relay for interrupting the steady energization of the line circuit for the associated signal block and energizing such line circuit by pulses of energy at a lirst or a second code rate according as the control relay associated with the next succeeding signal block is picked up or released, respectively;

(j) means responsive to the code following operation of each of the code following relays in each signal block, except the code following relay associated with the last track section in such block, for supplying pulses of train control energy across the rails of the exit end of the track section with which each respective code following relay is associated; and,

(k) means, including a back contact of the track relay for the last track section in each signal block and a front contact of the control relay associated with the next succeeding signal block, for supplying pulses of train control energy at said first code rate across the rails of the exit end of such last track section.

References Cited in the le of this patent UNITED STATES PATENTS 1,650,575 Wallace Nov. 22, 1927 2,337,173 Baughrnan Dec. 21, 1943 2,341,343 Tizzard Feb. 8, 1944 

1. APPARATUS FOR SUPPLYING TRAIN CONTROL ENERGY TO THE RAILS OF A STRETCH OF RAILWAY TRACK INCLUDING A SUCCESSION OF SIGNAL BLOCKS, SAID APPARATUS COMPRISING, IN COMBINATION: (A) A SERIES OF TRACK SECTIONS IN EACH SAID SIGNAL BLOCK, (B) A TRACK CIRCUIT INCLUDING A NORMALLY ENERGIZED TRACK RELAY FOR EACH SAID TRACK SECTION, (C) A CONTROL RELAY ASSOCIATED WITH THE ENTRANCE END OF EACH SIGNAL BLOCK, (D) A CODE FOLLOWING RELAY ASSOCIATED WITH THE EXIT END OF EACH TRACK SECTION, (E) A SOURCE OF DIRECT CURRENT ENERGY ASSOCIATED WITH THE EXIT END OF EACH SIGNAL BLOCK; (F) A TWO CONDUCTOR LINE CIRCUIT EXTENDING BETWEEN THE ENDS OF EACH OF SAID SIGNAL BLOCKS, EACH SAID CIRCUIT INCLUDING IN SERIES SAID SOURCE OF ENERGY ASSOCIATED WITH THE RESPECTIVE SIGNAL BLOCK, THE WINDINGS OF THE CONTROL RELAY AND AT LEAST ONE OF THE CODE FOLLOWING RELAYS ASSOCIATED WITH THE SIGNAL BLOCK, AND FRONT CONTACTS OF THE TRACK RELAYS FOR THE TRACK SECTIONS IN THE SIGNAL BLOCK, SUCH APPARATUS INCLUDED IN THE LINE CIRCUIT BEING SO PROPORTIONED THAT SO LONG AS THE WINDING OF THE CONTROL RELAY IS INCLUDED IN THE LINE CIRCUIT ONLY SUCH CONTROL RELAY BECOMES PICKED UP IN RESPONSE TO ENERGY FROM THE SOURCE ASSOCIATED WITH THE SIGNAL BLOCK; (G) MEANS INCLUDING A BACK CONTACT OF THE TRACK RELAY FOR EACH TRACK SECTION IN ONE OF SAID SIGNAL BLOCKS, EXCEPT THE LAST TRACK SECTION IN SUCH BLOCK, FOR BYPASSING THE WINDING OF THE CONTROL RELAY IN SAID LINE CIRCUIT FOR THAT SIGNAL BLOCK, THE APPARATUS INCLUDED IN THE LINE CIRCUIT BEING SO PROPORTIONED THAT THE REMAINING RELAYS INCLUDED IN SUCH CIRCUIT BECOME PICKED UP IN RESPONSE TO THE SOURCE OF ENERGY FOR THE SIGNAL BLOCK WHEN THE WINDING OF SUCH CONTROL RELAY IS BYPASSED; (H) A SLOW RELEASE RELAY ASSOCIATED WITH THE EXIT END OF SAID ONE SIGNAL BLOCK, (I) A CONTROL CIRCUIT FOR SAID SLOW RELEASE RELAY INCLUDING A FRONT CONTACT OF THE CODE FOLLOWING RELAY ASSOCIATED WITH THE LAST TRACK SECTION IN SAID ONE SIGNAL BLOCK; (J) MEANS CONTROLLED BY SAID SLOW RELEASE RELAY FOR INTERRUPTING THE STEADY ENERGIZATION OF THE LINE CIRCUIT FOR SAID ONE SIGNAL BLOCK AND ENERGIZING SUCH LINE CIRCUIT BY PULSES OF ENERGY AT A FIRST OR SECOND CODE RATE ACCORDING AS THE CONTROL RELAY ASSOCIATED WITH THE NEXT SUCCEEDING SIGNAL BLOCK IS PICKED UP OR RELEASED, RESPECTIVELY; (K) MEANS RESPONSIVE TO THE CODE FOLLOWING OPERATION OF EACH OF THE CODE FOLLOWING RELAYS IN SAID ONE SIGNAL BLOCK, EXCEPT THE CODE FOLLOWING RELAY ASSOCIATED WITH THE LAST TRACK SECTION IN SUCH BLOCK, FOR SUPPLYING PULSES OF TRAIN CONTROL ENERGY ACROSS THE RAILS OF THE EXIT END OF THE TRACK SECTION WITH WHICH EACH RESPECTIVE CODE FOLLOWING RELAY IS ASSOCIATED; AND, (L) MEANS, INCLUDING A BACK CONTACT OF THE TRACK RELAY FOR THE LAST TRACK SECTION IN SAID ONE SIGNAL BLOCK AND A FRONT CONTACT OF THE CONTROL RELAY ASSOCIATED WITH THE NEXT SUCCEEDING SIGNAL BLOCK, FOR SUPPLYING PULSES OF TRAIN CONTROL ENERGY AT SAID FIRST CODE RATE ACROSS THE RAILS OF THE EXIT END OF SUCH LAST TRACK SECTION. 